"When he went up for his last at-bat, I looked up at the scoreboard and saw his stats: 69 home runs, 144 RBIs, and I'm thinking, 'Look at that; that's not a season, that's a career.'" - Tom Lampkin, talking about Mark McGwire in his record-breaking season

Mark McGwire will be remembered as one of the key players during the "Steroid Era". During his first six full seasons in the Majors he averaged 36 homers. During his last four full seasons he averaged 61 per season. However, he achieved fame long before that, as a player at the University of Southern California, a participant on the 1984 Olympics baseball team, and a key player on the Oakland Athletics teams of the 1980s and 1990s.

"He hit a pop-up against us one day that went so high . . . all nine guys on our team called for it." - Marlins coach Rich Donnelly, about Mark McGwire

A big man at 6' 5", McGwire was drafted by the A's in the first round in 1984. He broke into the majors with them in 1986, appearing in 18 games and hitting .189. It was the year when Jose Canseco was Rookie of the Year. Also on the team that year were Dave Kingman and Dusty Baker, playing the last season of their careers. Tony LaRussa was the new manager of the team, in his first of ten years with the A's after having had a long stint with the Chicago White Sox.

In 1987, McGwire burst into the public's consciousness as Rookie of the Year himself. He set the record for most home runs by a rookie with 49, which lasted until 2017, when broken by Aaron Judge. Also on the team that year were Reggie Jackson and Ron Cey, playing out the last season of their careers.

In the next several seasons, McGwire developed a reputation as a slugger with a mediocre batting average. Even as the Oakland A's started winning the division regularly, McGwire's batting average dropped from .289 in 1987 to .260 in 1988, to .231 in 1989, to .235 in 1990, to .201 in 1991. As a result, his slugging percentage stayed under .500 from 1988 to 1991, though he was in the top 10 in 1989 and 1990. He also added a lot of value by drawing plenty of walks, leading the 1990 AL with 110. He was second or third in the AL in homers every season from 1988 through 1990.

The public was enamored of him and he was named to the All-Star Team every year from 1987 to 1992, before being skipped in 1993 and 1994, when he was injured. When healthy, the only All-Star team he missed was in his final season.

McGwire came back to greater prominence as a hitter in 1992, hitting 42 home runs with a batting average of .268, but teammate Eckersley was named both the American League MVP and also the Cy Young Award winner.

In 1993, McGwire got off to a great start, hitting .333 and slugging .726 in his first month, but then was injured and missed the rest of the year. He had an amazing 224 OPS+, a level he would never reach again. In 1994, he again had injuries and appeared in only 47 games. His performance was less impressive this time, hitting .252 with a slugging average of .474. In 1995, he again had injury issues, but appeared in 104 games, hitting 39 home runs. His 200 OPS+ would have led the league, but due to his limited playing time, he was not among the qualifiers.

1996 marked his last full year with the A's, and he made the most of it, hitting 52 home runs in only 130 games. He led the AL in slugging (.731), OPS (1198), homers, OPS+ (203) and OBP (.467) as the top hitter in the league; he was also in the top 10 in many other categories. On September 22nd, in a game against the Seattle Mariners, he became the eighth player to reach the upper deck in left field at the Kingdome when he hit a 473-foot home run to left center field in the 5th inning off Bob Wolcott; Jay Buhner had become the seventh the night before. He reached the upper deck again in that same inning when he took Matt Wagner deep to the same area of left center field, this time a 481-foot grand slam; Wagner was pitching in what would be his final Major League game. In between those two bombs, Scott Spiezio hit his first Major League home run, a three-run job off Rusty Meacham who did not record an out in that incredibly bizarre inning. Those three taters accounted for all eight Oakland runs the inning. In 1997, he started the season with Oakland and hit 34 home runs in 104 games, and then, after rumors had him being traded to many different teams, was sent to the St. Louis Cardinals on July 31st in return for Ps T.J. Mathews, Eric Ludwick and Blake Stein - a notoriously poor return for such a top-rank player. His 34 home runs before being traded are an all-time record; second is Adam Dunn with 32 in 2008, and third is Greg Vaughn with 31 in 1996.

Manager Tony LaRussa, McGwire's manager for so many years in Oakland, had moved to St. Louis in 1996, and the two were now reunited. With the Cardinals in 1997, McGwire added 24 home runs in 51 games, for a total of 58 home runs for the season. In 1997 he became the first player to hit 20 home runs in the same season with two different teams. He set a little-known record for the longest 2-year home run streak, homering in his last 2 games of 1997 and his first 4 games of 1998 (7 home runs in 6 games). His home runs in first four games of 1998 tied the record for most consecutive games homering at the start of a season (Willie Mays also had 4 for San Francisco Giants in 1971). Nelson Cruz and Chris Davis have since matched the mark.

In 1998, McGwire set the major league record with 70 home runs in a season; that record was broken by Barry Bonds in 2001. McGwire's chase of the home run record in 1998, with Sammy Sosa, is well-known, but what may not be as well-remembered is that he did not win the MVP award. In 1998 and 1999, when McGwire hit 70 and 65 home runs, St. Louis finished in third and fourth place respectively, and it was Sosa and Chipper Jones who won the MVP awards those two years.

There seemed to be relatively little awareness on the part of the public about steroids at that time, and when McGwire attributed part of his success to a legal substance called Androstendione, it was looked harshly upon by the press and mentioned frequently throughout the rest of the season. Manager Tony LaRussa attributed McGwire's performance to hard work. Pictures of McGwire often showed him with his adoring son, David, who was present when he broke Roger Maris' decades-old home run record of 61. Although Canseco later accused McGwire of using steroids, for years McGwire refused to say whether or not this was true.

McGwire's career, at such a peak in 1998 and 1999, was nearing its conclusion. In 2000, although he slugged .746, he appeared in only 89 games. That year, he set a record with 32 home runs, the most by a player who played in fewer than 100 games. In 2001, he hit .187 in 89 games and was done at the age of 37. As he was still drawing walks and hitting homers, his OPS+ was a respectable 106, but not good enough for a starting first baseman in the majors. That season, he set the major league record for most home runs (29) by a batter who failed to hit .200. While it was McGwire's last year with St. Louis, it was also the first year and Rookie of the Year season for Albert Pujols on the team.

Given the cloud of controversy surrounding him when he retired, McGwire did not immediately find another job within the game after he was done as a player, even though it was his intention to continue working in baseball in some capacity. He returned to the major leagues in 2010 as hitting coach of the St. Louis Cardinals under his former manager, Tony LaRussa and stayed on the job for three years, until the end of the 2012 season. That last year, he worked with another former teammate, Mike Matheny, who had succeeded LaRussa as manager of the Cards. Before taking the job as hitting coach, he gave a press conference in which he admitted taking steroids when he broke the single-season home run record, and apologized and expressed regrets for his actions. In 2013, he moved back to his home state of California as hitting coach of the Los Angeles Dodgers, whose manager was Don Mattingly. He left that job after Mattingly was dismissed following the 2015 season, but did not follow him to the Miami Marlins. Instead, he moved to the San Diego Padres as bench coach for first-year manager Andy Green in 2016.

During his career, which occurred before steroid use became a scandal, he was an immensely popular player. He was named to the All-Century Team in 1999, and around the same time Bill James named him the third greatest first baseman of all time (McGwire was, at the time, James' son's favorite player) as "Big Mac" had one of the top 15 OPS+es of all-time and ranked equally well on many other measures.

However, his place in history is considerably clouded, due largely because of his play during the steroid era and the long-held suspicion that he himself used these illegal substances. After refusing to talk about the issue when called before a Congressional committee hearing in 2005, he finally came clean in an interview on January 11, 2010, confirming that he had taken steroids for the first time in 1990, and then had taken steroids and human growth hormone regularly starting in 1993, including during his record-setting 1998 season. The tearful admission was prompted by his nomination a few months earlier as hitting coach of the Cardinals and the realization that he would be at the center of a media circus in spring training if he did not address the issue beforehand.

McGwire was seventh on the all-time home run list with 583 when he retired. He had "only" 1,414 RBI (which places him below Andres Galarraga, Joe Carter, and Rusty Staub, for example), 1,167 runs scored, 1,626 hits, and 262 doubles. McGwire was a true slugger: his ratio of 583 home runs to 1626 hits is by far the highest in major league history, with a hits per home run ratio of 2.8 or an average of .359 home runs per hit. Many of his counting stats are low due to a relatively brief career for an all-time star, plus injuries costing him over two seasons' worth of games. Additionally, his strength was not getting hits, but rather walks and homers. He does considerably better with career percentages, ranking tenth all-time in career slugging percentage (.588), twelfth in OPS and number one in career at-bats per home run (10.6). Expressed another way, he hit a home run in 9.4% of his at bats. He was the quickest player in major league history to reach 400 home runs (1,412 games) as well as 500 home runs (1,639 games). He also holds the record for the quickest 100 home runs in both the American League (393 games) and the National League (230 games). It should be mentioned that although McGwire's RBI totals are below several dozen other players during MLB's 100+ year history, his AB to RBI ratio is an impressive seventh all-time, just barely below Manny Ramirez in sixth place. His RBI per Game totals are equally as impressive. And his Runs Scored to Games ratio is phenomenal for a man who played first base, usually batted 4th or 5th in the order, and was a pure slugger. His RS/G ratio of .62 is on par with Hall of Fame second baseman Joe Morgan's, and just slightly below the ratios of both Willie Mays and Hank Aaron.

In terms of similarity scores, five of the ten most similar players at the end of 2005 were active and five were retired. The five retired players were Jose Canseco, Harmon Killebrew, Willie McCovey, Norm Cash, and Dave Kingman. That seemed to be a pretty good summary of McGwire's career: take the hard-hitting, high-walk, middle-of-the-road batting-average performance of Killebrew and Kingman, a solid glove at first and add in a dash of the stigma associated with Canseco, Bonds, Sosa, Palmeiro, etc.

McGwire and Co. may eventually be elected to the Hall of Fame, since the Hall can hardly leave out a whole generation of sluggers, and because the Hall has a history of letting in stigmatized players (there are a number of players in the Hall who threw spitballs or used corked bats or were accused of throwing games - although Shoeless Joe Jackson, remains excluded to this day, not to mention gambler Pete Rose). But it will be a while before his, or any of the other accused sluggers', luster is restored.

Bob Feller, in an interview around August 1, 2006, came out against McGwire being added to the Hall of Fame.

At least one sportswriter has opined that McGwire doesn't belong in the Hall of Fame even if you ignore any stigma. Stated Bob Rosen of the Elias Sports Bureau:

"I can't elect a guy for home run hitting alone. If a guy doesn't have 2,000 hits, unless he's a pitcher, or a guy who had a remarkable career that was ended by unfortunate circumstances, I can't vote for him."

Another sportswriter, Jim Hawkins, said something similar, only tied with the stigma:

"The one thing - the only thing - that makes him worthy of Cooperstown consideration is the home run total. And that statistic is so tainted, I can't take it seriously."

Such claims of one-dimensional performance ignore the fact that McGwire posted very good OBPs, drawing lots of walks in addition to his prodigious power, although the above-cited Hall of Fame voters likely did not place great value on walks.

In the fall of 2006, a poll was taken of baseball writers which indicated that McGwire may not get enough votes on the first ballot to even stay on the ballot. However, he did get over 20% of the vote in 2007, and so stayed on the ballot; the vote total was minuscule for a player who was a huge superstar and considered a lock for the Hall only a couple of years before, however. In Hall of Fame voting in 2008, he received 23.6% but in 2009 his percentage dropped slightly to 21.9%. In 2010 he was at 23.7%, the total being announced just before his public admission of steroid usage. He fell below 20% in 2011, getting 19.8%, then fell some more, to 19.5%, in 2012, in a year when almost all of the serious candidates for eventual election took big steps forward because of a weak first-year class of candidates. On the infamous "steroid ballot" in 2013, he finished with a total of barely 16.9% as voters clearly punished the group of players whose accomplishments were diminished by the taint of PED usage. He fell further in 2014, to 11% and did not make any significant progress over his final two years of eligibility, leading to his name being dropped from the ballot. In 2017, he was placed on the Veterans Committee ballot looking at players and executives from "Today's Game" era, but did not gain election. That year, he was inducted to the Cardinals' Hall of Fame.